We have undertaken the development of an in vitro system to check the efficacy of anticataract agents. This work has centered on the organ culture of rat lens. To check the viability of the rat lens prior to experimental manipulation, we developed a method to determine crystallin leakage from the lenses. This method, which provides a simple, yet accurate, indication of the integrity of the lens after dissection from the animal, has been checked by use of a radioactive tracer to show that the organ-cultured lens acts like a lens in vivo. Analysis of the proteins surrounding the lens indicates that a process of protein modification may occur around the lens in vivo. One way of investigating the lens changes occurring during cataract development is the use of two-dimensional gel electrophoresis of the parts of the lens. We have designed and developed a method to analyze small fractions of the rat lens to determine specific polypeptide changes that occur during cataract development. We have analyzed fractions from the epithelium and found the cell components most influenced by changes that signal cataract development. The organ culture system has been used to look at mechanisms to protect cells against oxidative damage. Enzymes involved in the one- and two-electron reduction of oxidative components have been investigated not only with whole lenses but also with cultured lens epithelial cells. It appears that the some of the enzymes involved in the detoxification of these oxidative compounds are specifically induced under conditions of oxidative stress. This work represents an integral part of the strategic plan for the Section on Cataracts.